managingtheriskofthe“betting-against-beta” anomaly ... · (“betting-against-beta” (bab))...
TRANSCRIPT
Managing the risk of the “betting-against-beta”
anomaly: does it pay to bet against beta?1
Pedro Barroso2 Paulo Maio3
First version: November 2016
1We are grateful to Kenneth French and Lasse Pedersen for providing stock marketreturn data.
2University of New South Wales. E-mail: [email protected] School of Economics, Department of Finance and Statistics. E-mail: paulof-
Abstract
We study the risk dynamics of the betting-against-beta anomaly. The strategy
shows strong and predictable time variation in risk and no risk-return trade-off. A
risk-managed strategy exploiting this achieves an annualized Sharpe ratio of 1.28
with a very high information ratio of 0.94 with respect to the original strategy.
Similar strategies for the market, size, value, profitability, and investment factors
achieve a much smaller information ratio of 0.15 on average. The large economic
benefits of risk-scaling are similar to those of momentum and set these two anoma-
lies apart from other equity factors. Decomposing risk into a market and a specific
component we find the specific component drives our results.
JEL classification: G11; G12; G17.
Keywords: Betting-against-beta, BAB, time-varying risk, realized volatility, mo-
mentum, risk factors, scaled factors, market anomalies.
1. Introduction
The capital asset pricing model (CAPM) of Sharpe (1964), Lintner (1965),
and Treynor (1965) provides the first theoretically motivated measure of the risk-
iness of each asset and the expected return it should command in equilibrium.
It is arguably the most taught asset pricing model and is widely used in corpo-
rate finance, portfolio performance measurement and investment valuation (see e.g.
Fama and French (2004) and Damodaran (2012)). However, we know from early
empirical tests of the model that low (high) beta stocks have consistently positive
(negative) risk-adjusted returns, a result known as the beta anomaly (Black et al.
(1972)). Recently, Frazzini and Pedersen (2014) propose an investment strategy
(“betting-against-beta” (BAB)) that exploits this anomaly by buying low-beta
stocks and shorting high-beta stocks. They report a Sharpe ratio for the strategy
of 0.78, about double that of the US equity market.
Besides US equities, Frazzini and Pedersen (2014) show that BAB achieves
abnormal returns in international equities, bonds, and currencies. Asness et al.
(2014b) and Baker et al. (2014) find similar results examining industry portfolios
and macro level country selection. Furthermore, in contrast to other anomalies
in equities, the profits of exploiting the beta anomaly seem robust to transaction
costs (Asness et al. (2014b)).
So the beta anomaly allows an impressive investment performance, at least
from an unconditional perspective. But Cederburg and O’Doherty (2016) find
that if one fully accounts for the time-varying systematic risk of the strategy its
alpha already becomes insignificant. We propose an alternative approach to the
conditional performance of the strategy and examine its time-varying volatility
1
instead.
There is an extensive literature documenting the time varying risk of the stock
market (e.g. Schwert (1989), Bollerslev (1987)) and the potential benefits of timing
its volatility (Fleming et al. (2001)). Barroso and Santa-Clara (2015) extend this
discussion to the space of long-short equity factor investing by showing the benefits
of managing the risk of momentum. More recently Moreira and Muir (2016) find
similar benefits of volatility timing for other equity factors.
We find that volatility has an important economic value to condition expo-
sure to the BAB strategy. In our sample, the Sharpe ratio of the BAB strategy
increases from 0.91 to 1.28 with risk-management. The information ratio of the
risk-managed strategy is 0.94 when compared to its original version, a result simi-
lar to that of momentum (0.93). The Fama-French 5-factor alpha of the strategy
increases from an annualized 5.48% to 15.97%. Similar to momentum, the benefits
come from strong predictability in risk and the absence of a risk-return trade-off.
In fact, we find months with extreme high risk for the strategy are followed by
lower returns on average.
Our results contrast with those of Cederburg and O’Doherty (2016). They
find that conditional on time-varying beta BAB is less of a puzzle. We find the
strategy also has strongly time-varying volatility and that using this to manage
its risk makes BAB a much deeper puzzle.
We decompose the risk of the strategy into specific and market risk to assess
the origins of the gains. We find that market risk plays a relatively minor role in
our results. The specific component is the one showing interesting predictability.
Our study is closely related to the literature on the conditional behaviour of the
beta anomaly. Cohen et al. (2005) find that consistent with the presence of money
2
illusion in the stock market, the required real discount rate on low-beta stocks
increases disproportionately with inflation. As a result the low-beta anomaly is
concentrated in periods with moderate to high inflation. Antoniou et al. (2015)
show that beta commands a reasonable risk premium in pessimistic periods and
show that the anomaly is mainly present at times of optimism. They suggest that
optimism attracts unsophisticated and overconfident investors to the market that
result in the mispricing of beta. Huang et al. (2015) examine a measure of excess
co-movement in the BAB portfolio as a proxy for arbitrage activity. They find
that periods of high activity predict short-term returns positively but also more
pronounced subsequent reversals. We add to this literature by examining the case
for timing the volatility of the strategy.
Our paper is also related to the recent literature on timing the volatility of
alternative equity factors. Moreira and Muir (2016) provide a comprehensive study
of such benefits but they do not examine BAB in the current version of their paper.
Therefore, to the best of our knowledge, our study is the first to document the
large economic benefits of managing the risk of BAB and its startling similarity
with those found for momentum.
This paper is structured as follows. Section 2. compares the performance of
BAB with that of other equity factors. Section 3. shows the performance of risk-
managed factor portfolios. Section 4. assesses the predictability of risk for the
strategy and the existence of a risk-return trade-off. In section 5. we examine a
decomposition of the risk of the strategy into its market and specific components.
Section 6. concludes.
3
2. Factor investing and betting-against-beta
In this section we describe the equity factors used in this study, provide de-
scriptive statistics of their investment performance, and examine the risk-adjusted
performance of betting-against-beta (BAB).
We use the BAB returns for US stocks obtained from AQR’s data library
(https : //www.aqr.com/library/data − sets). The strategy consists on buying
low-beta stocks and shorting high-beta stocks choosing weights such that the ex-
ante beta of the strategy is zero. This implies having more than one dollar in the
long leg and less than one dollar in the short leg. The difference is funded by a
short position in the risk-free rate asset (T-bills) such that the overall portfolio
has zero cost. Frazzini and Pedersen (2014) provide a complete description of the
construction of the strategy’s portfolio.
We compare the returns of BAB with those of the Fama and French (1993)
three factors (FF3 model). The FF3 factors are: i) the excess return of the market
over the risk-free rate (market factor or ‘RM’); ii) the return of small firms in
excess of large firms (size factor or ‘SMB’); iii) the return of high book-to-market
stocks in excess of low book-to-market stocks (value factor or ‘HML’). For com-
pleteness we add to these the two newly proposed factors in Fama and French
(2015) (FF5 model): operating profitability (‘RMW’ for robust-minus-weak) and
investment (‘CMA’ for conservative-minus-aggressive). These two factors capture,
respectively, the average positive excess returns of firms with high profitability and
of those with low investments (as measured by asset growth). Taken together these
factors reflect the sources of predictability for the cross section of equity returns
found in the size (Banz (1981)), value (Basu (1983), Bondt and Thaler (1985),
4
Rosenberg et al. (1985)), profitability (Novy-Marx (2013), Hou et al. (2014)), and
investment (Hou et al. (2014)) variables.
We also use the Carhart (1997) 4-factor model (C4 model) that combines mo-
mentum with the FF3 factors. The return of momentum in a given month t is
defined as the difference in value-weighted returns between the portfolio of previous
winners and the portfolio of previous losers. The previous winners are the stocks
in the top decile according to cumulative return from months t− 12 to t− 2 while
the previous losers are those in the bottom decile. Only stocks listed in NYSE are
used to compute the cut-off points of the deciles. This avoids having some of the
deciles dominated by many small caps. The month t− 1 is skipped to avoid con-
founding with the short-term reversal effect in monthly returns (Jegadeesh (1990),
Jegadeesh and Titman (1995)). Momentum returns capture the tendency of recent
winners, as defined by their returns in the previous 3 to 12 months, to continue
outperforming recent losers (Levy (1967), Jegadeesh and Titman (1993)).
The returns of the momentum portfolios and the FF5 factors are from Kenneth
French’s data library.1 We have both daily and monthly returns available for all
factors from July 1963 to December 2015. We use realized volatilities computed
from one month and 6 months of data to perform the risk-scaling so our first
risk-managed returns start in January 1964 and end in December 2015.
[Insert table 1 near here]
Table 1 shows the descriptive statistics of each factor-based investment strategy.
Compared with the market, size, value, momentum, profitability, and investment
factors, BAB has the highest Sharpe ratio. Its annualized Sharpe ratio is of 0.91,
1http : //mba.tuck.dartmouth.edu/pages/faculty/ken.french/datalibrary.html
5
more than double the 0.38 of the market with is already a central puzzle in financial
economics (Mehra and Prescott (1985)). It is also higher than the Sharpe ratio
of momentum (0.67) which is often regarded has the major asset pricing anomaly.
This illustrates the extent of the empirical failure of the CAPM. Black et al. (1972)
find that the security market line (SML) is flatter than what should hold accord-
ing to the CAPM. Frazzini and Pedersen (2014) show that a strategy exploiting
this apparent mispricing has an economic performance even more impressive than
momentum.
The strategy’s high Sharpe ratio comes with a considerable higher order risk
though with an excess kurtosis of 3.58 combined with a skewness of -0.62, both
higher in absolute terms than the market that has 1.90 and -0.52 respectively. This
higher order risk is small though when compared to the very high excess kurtosis
of momentum (7.84) and respective negative skewness (-1.42).
In spite of the impressive long run performance of the strategy it is also ex-
posed to substantial downside risk. Its maximum drawdown of -52.03 is close in
magnitude to that of the market (-55.71) which has a much higher standard de-
viation (15.45% versus 11.21%). Still, both the higher order risk and the (closely
related) maximum drawdown are smaller than those of momentum. So BAB of-
fers a higher Sharpe ratio and it is not as exposed to crashes as momentum (see
Daniel and Moskowitz (2016), Barroso and Santa-Clara (2015) for a discussion of
the crash risk of momentum).
Table 2 examines the ability of other risk factors to explain the returns of BAB.
The second column shows the alpha of the strategy with respect to the different
risk models. Columns 3 to 8 show the factor loadings of the strategy.
The market factor does not explain the returns of BAB. The strategy has a
6
high annualized alpha of 10.54% with a t-statistic of 6.57. The beta of the strategy
is very close to zero (-0.06). This shows that the strategy, which is constructed to
have an ex-ante beta of zero, on average achieves this goal ex-post.
Jointly the size and value factors explain approximately 20% of the CAPM-
alpha of the strategy. This is mainly due to the value factor. The BAB strategy in
all specifications that include the value factor shows a significant exposure to that
factor. The strategy is also exposed to the momentum, profitability and investment
factors. Taken together we see that available stock market risk models explain up
to 48% of the CAPM-alpha of the strategy (1−5.48/10.54). This happens because
on average low beta firms also show some loading on value, profitability and (low)
investment factors.
This suggests that a substantial part of the empirical failure of the CAPM can
be traced to failing to capture the multi-dimensional nature of risk that features
in latter models.2. But this ability of other factors to explain approximately half
of the anomaly’s risk-adjusted returns still leaves a considerable amount to be
explained. The alpha of approximately 5.5 to 6 percentage points a year and
respective t-statistics (3.49 in the C4 model and 3.48 in the FF5 model) are clearly
economically and statistically significant.
[Insert table 2 near here]
3. Scaled factor strategies
Barroso and Santa-Clara (2015) construct a risk-scaled version of momentum.
2It also suggests a possible reason for the particularly high Sharpe ratio of the strategy: it isanalogous to a linear combination of weakly correlated stock market factors
7
We extend this to other factors and examine the resulting economic performance
for an unconstrained investor. We compute the realized variance RVF,t from daily
returns in the previous 21 sessions for each month and factor. Let {rd}Dd=1
be the
daily returns and {dt}Tt=1 the time series of the dates of the last trading sessions
of each month. Then the realized variance of factor F in month t is:
RVF,t =
20∑
j=0
r2F,dt−j. (1)
Then we use the realized volatility σ̂F,t =√
RVF,t to scale the returns in order
to achieve a given target σtarget. Implicitly σ̂F,t is used as the forecast of σF,t+1.
All of the original factors used are zero-cost portfolios, so their scaled versions are
still zero-cost and self financing strategies that we can scale without constraints.
The scaled portfolio weight in the original factor at time t is:
Wt =σtarget
σ̂F,t
(2)
And so the risk-scaled factors are defined as F ∗
t+1 = Ft+1Wt. The choice of
volatility target is arbitrary but influences directly the maximum, minimum, mean
and the standard deviation of returns as well as the maximum drawdown of the
scaled portfolio. However this choice is irrelevant for scale-invariant measures
of portfolio performance such as the Sharpe ratio, (left) skewness, and excess
kurtosis. As in Barroso and Santa-Clara (2015) we pick a target corresponding to
an annualized volatility of 12%. This choice of target has the desirable property of
producing scaled factor portfolios with approximately the same ex-post volatility
of the (unscaled) US stock market. Picking the same target for all portfolios
facilitates comparison of those performance measures that are sensible to scaling.
8
Other volatility models could produce more accurate estimates of risk with
increased potential for risk-scaling. We refrain from that pursuit in this paper
and chose to focus instead on this somehow coarse measure of volatility. This also
serves as an implicit control mechanism when assessing the existence of robust
economic benefits in risk-scaling.3
[Insert table 3 near here]
Table 3 shows the performance of the scaled factors. Risk-scaling has economic
gains for investors following (almost) all factor strategies. For the market, the
risk-scaled factor has an information ratio of 0.20 with respect to the unscaled
factor. This gain confirms the result of Fleming et al. (2001) who document the
economic benefits of timing the volatility of the market. Their documented gains
from market timing using volatility contrast with the difficulty of similar strategies
trying to use predictability in returns (Goyal and Welch (2008)).
The benefits are not restricted to the market factor as 6 out of the 7 portfolios
show positive information ratios. The exception is the size premium for which the
scaled factor has a negative information ratio. Moskowitz (2003) show that the
size premium increases with volatility and recessions in a way consistent with a
risk-based explanation. Our results are consistent with theirs for the size factor.
By far the most impressive gains are found for the momentum and BAB factors.
Comparing with table 1 the Sharpe ratio of momentum increases from 0.67 to 1.08
(a 0.41 gain) and that of BAB increases from 0.91 to 1.28 (a 0.37 gain). The
information ratio of the scaled strategies with respect to their original versions
are very large for these two factors: 0.93 for MOM* and 0.94 for BAB*. These
3As a robustness test we also use the usual workhorse of volatility modelling, the GARCH(1,1).We present those results in table 6.
9
high information ratios reflect the fact that the risk-scaled portfolios are highly
correlated with the original factors but much more profitable. For the FF5 factors
the information ratio is on average 0.15, momentum and BAB have information
ratios about 6 times larger. Our results for momentum confirm the findings of
Barroso and Santa-Clara (2015). Moreira and Muir (2016) recently examine the
benefits of risk management in a set of factors that includes the FF5 but do not
consider BAB. Therefore, to the best of our knowledge, we are the first to document
that BAB shares this puzzling feature with momentum: the two strategies have
particularly expressive economic benefits from risk management, gains that set
them both apart from the FF5 factors.
[Insert table 4 near here]
Table 4 shows the risk-adjusted performance of BAB*. The strategy has a very
high CAPM-alpha of 21.10% per year. The risk model with the best fit for the strat-
egy is the C4 that explains 25% of its CAPM-alpha ((21.10%-15.83%)/21.10%).
This is a smaller proportion than the almost half explained in table 2. So risk-
managed BAB offers more diversification benefits than BAB for diversified in-
vestors exposed to other equity factors. The smallest annualized alpha is a very
high 15.83% (with the C4 model) and the adjusted r-squares of the regressions
are all smaller than in table 2. This confirms that BAB* is of value for diversified
investors and more so than BAB.
[Insert figure 1 near here]
Figure 1 shows the cumulative returns of momentum, betting-against-beta and
their respective risk-managed versions. As the strategies considered are zero-cost
10
portfolios their returns are excess returns. In order to have gross returns we add
to each strategy the gross return of an investment in the risk-free rate. So each
moment in time the portfolio puts all wealth in the risk-free rate and combines
this with a long-short portfolio. 4
In a pure CAPM world none of the strategies in figure 1 should have any
drift but empirically they have had an impressive economic performance. One
US dollar invested in momentum in July 1963 grows to 9, 990 by the end of the
sample. For the betting-against beta strategy the investment grows to a more
modest amount of 1, 675 dollars but with much less risk than the momentum
strategy. The scaled strategies have similar ex post standard deviation (17.37 for
MOM* versus 16.84 for BAB*) but very different end results: the investment in
risk-managed momentum grows to 87, 843 but in the beta anomaly to 364, 121.
For comparison a similar investment in the US stock market grows to 139 US
dollars by the end of the sample. This illustrates with an investment approach
the extent of the puzzle in the performance of these strategies, particularly the
benefits derived from managing their risk. A related debate is whether investors
could attain these performances in a realistic setting with transactions costs and
other frictions (see for example Lesmond et al. (2004) and Asness et al. (2014a)
for different interpretations of the evidence).
We do not address this debate directly but one possible interpretation of our
results is that the economic performance of these strategies, without frictions,
seems too puzzling to accept any explanation that does not incorporate them.
4For example, for momentum the original strategy puts a notional amount in the long leg ofWealtht and in the short leg of −Wealtht. For the risk-managed version the notional amountwould be WtWealtht and −WtWealtht in the long and short legs respectively. For BAB theamounts in the long and short leg are different in order to target a beta of zero but they areoffset by positions in the T-bills.
11
From an asset pricing perspective it is relevant to distinguish between correct
prices driven by risk loadings from mispricings that are hard to arbitrage. The
sizeable benefits of risk-management for BAB deepen the puzzle of the anomaly
and provide further indirect evidence of its relation to explanations relying on
arbitrage and frictions.
3.1. Robustness test: GARCH (1,1)
We assess the robustness of our results with respect to the horizon used to
compute the realized variance and using the GARCH(1,1) instead to estimate
variance.
Table 5 shows the performance of scaled factors using 6 months to estimate
variance instead of just one. First we note that for this particular window the
result of the economic value of timing the volatility of the market is not robust.
[Insert table 5 near here]
The information ratio for risk-managed momentum is 0.98, so the benefits for
this strategy are robust to this alternative period to compute variance. For BAB,
with a Sharpe ratio of 1.17 and an information ratio of 0.76 with respect to the
original strategy, we conclude that the benefits of risk-management are robust to
using an alternative window.
We also use GARCH(1,1) from monthly returns of each strategy to compute
risk-managed strategies. In order to assess the benefits of risk-management in
a realistic OOS environment we only use volatility estimates obtained from a
GARCH(1,1) model estimated in real time. We use the initial 120 months of
data to infer the parameters of the initial model and use them to make a forecast
12
for month 121. The following month we expand the sample with a new observation
and re-estimate the model. We keep re-iterating the procedure until the end of the
sample. Table 6 shows the economic performance of the risk-managed portfolios.
For comparison table 7 shows the performance of the original strategies for this
different sample period.
[Insert tables 6 and 7 near here]
In this setting the benefits of risk-management for the market are not robust
with a negative information ratio of -0.18. For momentum the benefits are robust
with a gain in Sharpe ratio from 0.57 to 0.71 and a substantial reduction in the
maximum drawdown from -80.36% to just -31.88%. For BAB the results are quite
robust. The information ratio of BAB* is 0.65, even higher than the 0.43 of MOM*.
So in this particular exercise the benefits of risk-management for BAB are stronger
than for MOM.
4. Risk and return of BAB
We examine the predictability of the risk of BAB and its relation with expected
returns.
First we examine the predictability of risk. Figure 2 shows the time series of
the (annualized) monthly realized variances computed from daily returns.
[Insert figure 2 near here]
The plot illustrates the typical patterns of volatility known from Bollerslev
(1987), Schwert (1989) and many others. Namely, volatility varies over time in a
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persistent manner. The realized volatility of the strategy varies significantly from a
minimum of 1.75% in April 1965 to a maximum of 83% reached in May 2002. The
series is also highly non-normal with a kurtosis of 35.44 and a very high positive
skewness of 4.52 indicating that the sample contains extreme high risk outliers.
To examine the predictability of risk we run the regression:
1
ˆσi,t+1
= ρ0 + ρ11
σ̂i,t
+ εt+1. (3)
We focus on the inverse of realized volatility for two reasons. First, the risk-
managed strategy puts a weight on BAB proportional to this quantity so it is
the variable of direct interest to understand the source of the gains. Second, the
sample of the inverse of volatilities is much closer to normal. It has a kurtosis of
2.99 and a skewness of -0.11, this allows for a much better inference reducing the
large weight of outliers in the fit.
Table 8 shows the results of regression 3. Given the similar gains of risk manage-
ments for BAB and momentum we focus on these two strategies for the remainder
of the paper.
[Insert table 8 near here]
The table shows that both series have similar levels of predictability. The slope
coefficient is positive and it has a t-statistic of 23.88 for BAB and 25.31 for MOM.
This shows that safe months tend to follow safe months. Most of the variation in
the dependent variable is explained by its lagged value (R2 of 60.79% for BAB and
56.11% for MOM).
But in sample predictability can be misleading and so we also compute the out-
of-sample (OOS) R2 of the regression. For that purpose we use an initial window S
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of 120 months ro run the first in-sample regression and use this to make a forecast
for month S + 1 that we compare with the ex-post realized value of the variable.
The following month we use an expanding window to estimate the regression and
re-iterate the procedure until the end of the sample. The OOS R2 for a factor i is
estimated as:
R2
i,OOS = 1−
T−1∑t=S
(ρ̂0,t + ρ̂1,t1̂/σi,t − ̂1/σi,t+1
T−1∑t=S
(1̂/σi,t − ̂1/σi,t+1)2, (4)
where 1̂/σi,t is the historical average up to time t and both α̂t and ρ̂t are
estimated with information available only up to time t. A positive OOS R2 shows
that on average the forecast from the regression outperforms that obtained from
the historical average.
We find the OOS R2 for BAB is not only positive but also very close to its
in-sample counterpart. This shows that the regression shows strong robustness out-
of-sample – a stark contrast with similar regressions for the equity premium that
typically achieve negative OOS R2’s (Goyal and Welch (2008)). The predictability
of the (inverse of) realized volatility for BAB is quite similar to the one documented
for momentum.
[Insert table 9 near here]
We next examine if this predictability in risk is related with expected returns.
For this purpose we regress the returns of each strategy on its lagged (inverse of)
realized volatility.
15
ri,t+1 = γ0 + γ1(1/σ̂i,t) + ηt+1. (5)
The existence of a risk-return trade-off should be captured by a statistically
significant negative γ1 meaning that months with less risk for the strategy also
predict smaller returns. The results in table 9 show there is no evidence of any
predictability of risk for the returns of BAB (or momentum). In fact the point
estimates for both strategies are positive, although not statistically significant.
[Insert figure 3 near here]
In figure 3 we further examine the relation between risk and return for the
strategies. For each strategy, we sort all months into quintiles according to realized
volatility. Then, for each quintile, we take the subset of months subsequent to
those in that quintile and compute the average return, standard deviation, and
Sharpe ratio over that subset. The results for momentum confirm the pattern in
Barroso and Santa-Clara (2015) that higher risk predicts both lower returns and
higher risk for the strategy, so the Sharpe ratio of the strategy is much higher
following quintiles 1 to 3 than in the two top quintiles. The results for BAB
show a similar pattern. In panel A the returns following a month in quintile 5
are lower (4.84%) on average than for other quintiles (11.53%). The relation is
not monotonous and the underperformance of BAB in terms of expected returns
is concentrated in months of particularly high risk. On the other hand, panel B
shows that subsequent risk rises monotonically with lagged risk. The annualized
volatility is 5.13% after a month in quintile 1 and it is 19.06% after a month in
quintile 5. As a result the Sharpe ratio is much smaller after months in the top
quintile (0.25) versus months after the lowest quintile (1.83). Both effects combine
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such that BAB has a quite weak performance as a factor subsequent to months of
very high risk.
[Insert figure 4 near here]
Figure 4 shows the weights of BAB* and MOM*. On average BAB* has a
higher weight than MOM*. This happens because both strategies target the same
volatility but original BAB has a much lower standard deviation than MOM.5 As
the choice of target volatility is arbitrary this difference in the average weight is not
very informative. We note though that the two series have a strong and statistically
significant correlation of 0.63 (at the 1%) level. So an hypothetical unconstrained
arbitrageur following both strategies simultaneously would see speculative capital
being absorbed and freed-up from these two uses at the same time. This suggests
a possible limit to arbitrage for risk-management.
5. Anatomy of BAB risk
Grundy and Martin (2001) show that the beta of momentum with respect to
the market varies substantially over time. Cederburg and O’Doherty (2016) argue
that the conditional beta of BAB explains its premium. Motivated by this we
examine if time-varying systematic risk can account for the similar gains of risk
management for BAB and MOM and the performance of BAB in particular.
[Insert figure 5 near here]
5A version of BAB* re-scaled to have a similar average weight as MOM* would also show avery similar standard deviation in weights, so the apparent wilder swings of the weights in BABare only due to a level effect.
17
Figure 5 shows the plot of the time series of monthly betas of BAB and MOM
with respect to the market. The results for momentum confirm Grundy and Martin
(2001). The beta of MOM ranges between -2.86 and 2.57. We find that BAB also
has some time-varying market risk. In spite of being deliberately constructed to be
market neutral, its beta ranges between -1.57 and 0.30 and it shows some persis-
tence. Still the beta of BAB shows relatively little time-variation when compared
to momentum.
We use the CAPM to decompose the risk of BAB and MOM into a market and
a specific component:
RVF,t = β2
tRVRM,t + σ2
ε,t. (6)
The realized variances are estimated from daily returns in each month. 6 We
find that on average 37% of the risk of BAB is systematic, so the market neutral
strategy has a substantial market risk component. To assert the origin of the
gains, we examine the performance of a risk-managed strategy using each of the
risk components separately.
[Insert table 10 near here]
Table 10 shows the performance of risk-scaled BAB and momentum with total
risk, specific risk, and market risk respectively. The Sharpe ratio of BAB scaled
with specific risk is 1.21, close to the one using total risk (1.32). By contrast,
the strategy using the systematic risk has a very low Sharpe ratio of 0.18 and
6To ensure the decomposition holds exactly, we use in this section the variance formula. Thisde-means returns each month instead of just summing the squares of returns as in equation1. This does not change any of the results substantially and avoids the possibility of getting anegative specific risk.
18
a extreme value for standard deviation (3898.63), excess kurtosis (610.79), and
skewness (24.68). The results for momentum are similar to those of BAB. They
both show that the gains of risk-management come from using the informational
content in the specific component of risk.
We also examine the predictability of the inverse of each component of risk.
Table 11 shows the results of an auto-regression for each of those components
(which correspond to the weights in the strategies examined in table 10).
[Insert table 11 near here]
For BAB the specific part of risk is highly persistent with a slope coefficient
of 0.68 and a t-statistic of 20.30. The regression shows a good fit both in-sample
and OOS with R-squares of 46.13% and 47.46% respectively. The predictability
of the specific component is almost as high as that of total risk. For the sys-
tematic component there is no predictability. The slope coefficient is zero and
so is the R-squared. The results for momentum are similar and confirm those of
Barroso and Santa-Clara (2015). For both strategies the predictable part of risk
is the specific component.
6. Conclusion
Approximately half of the risk-adjusted returns of betting-against-beta with
respect to the market are explained by the Carhart (1997) or the Fama and French
(2015) factor models. While the remainder risk-adjusted performance is still a
puzzle in its own right, managing the risk of the strategy makes it much larger.
The risk-managed strategy has a high information ratio of 0.94, similar to that of
19
momentum. The scaled BAB has a higher alpha with respect to the market and
less of it (only 25%) is explained by equity risk factors. So managing the risk of
BAB creates and economic value orthogonal to those equity factors and even the
original BAB itself.
Risk is highly predictable for BAB, similar to that of momentum. There is also
no evidence of a risk-return trade-off for the strategy. If anything there seems to
be the opposite of a trade-off: BAB generally performs worse after months of high
risk in the strategy. This bad performance is concentrated in periods of extreme
risk for the strategy suggesting a regime switch in high volatility states.
Time-varying systematic risk has been proposed as an explanation of the pre-
mium of BAB (Cederburg and O’Doherty (2016)). We find evidence confirming
the existence of this time-varying systematic risk but also find that it conveys rela-
tively little information about the conditional performance of the strategy. Decom-
posing the risk of BAB into market and specific risk we find that the predictable
part is the specific one. Also, the performance of a strategy scaled by specific risk
only is very similar to one using total risk. So we conclude that specific risk is
causing the gains of risk management.
Generally, our results show that risk-managed BAB is a deeper puzzle than its
original version. The informational content of its own lagged volatility to condition
exposure to the strategy is very large, similar to momentum and much higher than
that found for the other equity factors examined.
The results are robust to using a different window to compute volatilities or a
GARCH(1,1) model to estimate it.
20
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Table 1Performance of factor-based strategies
The performance of the betting-against-beta factor (BAB) is compared with the
Fama-French-Carhart risk factors: market (RMRF), size (SMB), value (HML), momen-
tum (MOM), profitability (RMW), and investment (CMA). All statistics are computed
with monthly returns. Reported are the maximum and minimum one-month returns
observed in the sample, the mean average excess return (annualized), the (annualized)
standard deviation of each factor, excess kurtosis, skewness, (annualized) Sharpe ratio,
and the maximum drawdown (MDD). The sample returns are from 1964:01 to 2015:12.
The max, min, mean, standard deviation and maximum drawdown are in percentage
points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe MDDRMRF 16.10 -23.24 5.92 15.45 1.90 -0.52 0.38 -55.71SMB 22.32 -16.70 2.89 10.79 5.64 0.53 0.27 -52.82HML 13.91 -13.11 4.04 9.94 2.61 0.01 0.41 -45.21MOM 26.16 -45.79 16.23 24.26 7.84 -1.42 0.67 -80.36RMW 12.19 -17.57 2.94 7.38 11.55 -0.40 0.40 -39.17CMA 9.51 -6.81 3.69 6.98 1.65 0.29 0.53 -17.62BAB 12.89 -15.22 10.19 11.21 3.58 -0.62 0.91 -52.03
26
Table 2Alphas for BAB
This table presents the alphas and factor loadings from time-series regressions of
the betting-against-beta factor (BAB). The factor models are the CAPM, Fama-French
three-factor model (FF3), Carhart’s four-factor model (C4), and the Fama-French five-
factor model (FF5). The factors are the market (RM), size (SMB), value (HML), mo-
mentum (MOM), profitability (RMW), and investment (CMA). The sample is 1964:01
to 2015:12. For each regression, the first row presents the coefficient estimates and the
second row reports Heteroskedasticity-adjusted t-ratios (in parentheses). α is the an-
nualized intercept. R2 denotes the adjusted coefficient of determination. Bold t-ratios
indicate statistical significance at the 5% level.
Model α(%) βRM βSMB βHML βMOM βRMW βCMA R2(%)CAPM 10.54 −0.06 0.51
(6.57) (−1.25)FF3 8.26 0.03 −0.01 0.44 14.31
(5.27) (0.56) (−0.10) (6.46)C4 5.97 0.07 0.00 0.50 0.11 19.64
(3.49) (1.40) (0.01) (7.06) (4.10)FF5 5.48 0.08 0.11 0.28 0.46 0.38 22.00
(3.48) (1.76) (2.17) (3.06) (5.90) (3.21)
27
Table 3Performance of scaled factor strategies
The performance of the scaled betting-against-beta factor (BAB*) is compared with
the Fama-French-Carhart scaled risk factors: market (RMRF*), size (SMB*), value
(HML*), momentum (MOM*), profitability (RMW*), and investment (CMA*). Each
scaled factor uses the realized variance in the previous month to scale the exposure to
the original factor. All statistics are computed with monthly returns. Reported are the
maximum and minimum one-month returns observed in the sample, the mean average
excess return (annualized), the (annualized) standard deviation of each factor, excess
kurtosis, skewness, (annualized) Sharpe ratio, and the maximum drawdown (MDD).
IR denotes the (annualized) information ratio of the scaled factor with respect to the
unscaled benchmark. The sample returns are from 1964:01 to 2015:12. The max, min,
mean, standard deviation and maximum drawdown are in percentage points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe IR MDDRMRF* 13.94 -18.66 6.30 14.63 1.14 -0.27 0.43 0.20 -52.82SMB* 23.60 -22.94 4.21 18.86 1.85 -0.10 0.22 -0.04 -84.68HML* 22.84 -22.78 8.41 18.67 1.19 0.15 0.45 0.20 -57.42MOM* 20.74 -15.43 18.79 17.37 0.82 -0.17 1.08 0.93 -37.33RMW* 18.26 -17.15 8.65 17.14 0.49 0.03 0.50 0.31 -57.97CMA* 18.22 -13.84 8.15 16.24 0.07 0.17 0.50 0.07 -44.02BAB* 17.59 -28.54 21.48 16.84 2.70 -0.41 1.28 0.94 -56.75
28
Table 4Alphas for scaled BAB
This table presents the alphas and factor loadings from time-series regressions of
the scaled betting-against-beta factor (BAB*). BAB* uses the realized variance in the
previous month to scale the exposure to the original factor. The factor models are the
CAPM, Fama-French three-factor model (FF3), Carhart’s four-factor model (C4), and
the Fama-French five-factor model (FF5). The factors are the market (RM), size (SMB),
value (HML), momentum (MOM), profitability (RMW), and investment (CMA). The
sample is 1964:01 to 2015:12. For each regression, the first row presents the coefficient
estimates and the second row reports Heteroskedasticity-adjusted t-ratios (in parenthe-
ses). α is the annualized intercept. R2 denotes the adjusted coefficient of determination.
Bold t-ratios indicate statistical significance at the 5% level.
Model α(%) βRM βSMB βHML βMOM βRMW βCMA R2(%)CAPM 21.10 0.06 0.19
(8.75) (0.90)FF3 18.22 0.16 0.03 0.55 9.22
(7.68) (2.33) (0.45) (7.66)C4 15.83 0.20 0.04 0.61 0.12 11.75
(6.42) (2.87) (0.54) (8.39) (4.04)FF5 15.97 0.22 0.10 0.35 0.30 0.44 11.14
(6.34) (2.93) (1.33) (3.66) (2.96) (2.83)
29
60 65 70 75 80 85 90 95 00 05 10 15 2010
0
101
102
103
104
105
106
Cumulative returns
MOMBABMOM*BAB*
Fig. 1. The cumulative returns of BAB, MOM and its risk-managed versionsusing the previous month realized volatility. The returns are from 1964:01 to2015:12 and include the return of the risk-free rate asset plus the excess return ofthe respective zero-cost portfolio.
30
Table 5Performance of scaled factor strategies: alternative variance measures
The performance of the scaled betting-against-beta factor (BAB*) is compared with
the Fama-French-Carhart scaled risk factors: market (RMRF*), size (SMB*), value
(HML*), momentum (MOM*), profitability (RMW*), and investment (CMA*). Each
scaled factor uses the realized variance in the previous six months to scale the exposure to
the original factor. All statistics are computed with monthly returns. Reported are the
maximum and minimum one-month returns observed in the sample, the mean average
excess return (annualized), the (annualized) standard deviation of each factor, excess
kurtosis, skewness, (annualized) Sharpe ratio, and the maximum drawdown (MDD).
IR denotes the (annualized) information ratio of the scaled factor with respect to the
unscaled benchmark. The sample returns are from 1964:01 to 2015:12. The max, min,
mean, standard deviation and maximum drawdown are in percentage points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe IR MDDRMRF* 11.39 -20.35 4.99 13.99 1.64 -0.57 0.36 0.00 -57.36SMB* 21.79 -21.52 4.34 17.96 1.50 0.11 0.24 -0.02 -82.76HML* 23.13 -17.50 7.41 17.78 0.92 0.12 0.42 0.12 -55.81MOM* 21.74 -17.06 18.67 17.04 1.18 -0.15 1.10 0.98 -28.28RMW* 15.82 -24.01 7.63 16.65 1.10 -0.19 0.46 0.23 -62.33CMA* 13.77 -14.23 8.38 15.63 -0.07 0.16 0.54 0.14 -37.14BAB* 18.25 -22.79 19.16 16.38 1.63 -0.43 1.17 0.76 -57.14
31
Table 6Performance of scaled factor strategies: GARCH(1,1)
The performance of the scaled betting-against-beta factor (BAB*) is compared with
the Fama-French-Carhart scaled risk factors: market (RMRF*), size (SMB*), value
(HML*), momentum (MOM*), profitability (RMW*), and investment (CMA*). Each
scaled factor uses the volatility forecast obtained from a GARCH(1,1) model to scale
the exposure to the original factor. All statistics are computed with monthly returns.
Reported are the maximum and minimum one-month returns observed in the sample,
the mean average excess return (annualized), the (annualized) standard deviation of each
factor, excess kurtosis, skewness, (annualized) Sharpe ratio, and the maximum drawdown
(MDD). IR denotes the (annualized) information ratio of the scaled factor with respect
to the unscaled benchmark. The sample returns are from 1963:07 to 2015:12, while the
first volatility forecast and scaled factor observation occurs for 1973:07. The max, min,
mean, standard deviation and maximum drawdown are in percentage points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe IR MDDRMRF* 9.14 -18.52 4.49 12.24 2.25 -0.75 0.37 -0.18 -42.77SMB* 16.83 -13.35 3.01 11.96 1.75 0.14 0.25 0.02 -62.68HML* 12.87 -11.67 3.79 12.23 0.73 -0.13 0.31 -0.18 -48.07MOM* 12.94 -27.62 9.99 13.99 6.31 -1.22 0.71 0.43 -31.88RMW* 9.54 -18.18 5.91 12.64 1.78 -0.45 0.47 0.19 -57.12CMA* 9.53 -9.80 6.76 11.75 -0.13 0.04 0.58 0.01 -31.88BAB* 14.49 -18.18 14.58 13.18 2.37 -0.71 1.11 0.65 -54.01
32
Table 7Performance of factor-based strategies: 1973:07–2015:12
The performance of the betting-against-beta factor (BAB) is compared with the
Fama-French-Carhart risk factors: market (RMRF), size (SMB), value (HML), momen-
tum (MOM), profitability (RMW), and investment (CMA). All statistics are computed
with monthly returns. Reported are the maximum and minimum one-month returns
observed in the sample, the mean average excess return (annualized), the (annualized)
standard deviation of each factor, excess kurtosis, skewness, (annualized) Sharpe ratio,
and the maximum drawdown (MDD). The sample returns are from 1973:07 to 2015:12.
The max, min, mean, standard deviation and maximum drawdown are in percentage
points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe MDDRMRF 16.10 -23.24 6.71 15.94 2.00 -0.56 0.42 -54.36SMB 22.32 -16.70 2.94 10.78 6.96 0.59 0.27 -52.82HML 13.91 -13.11 3.94 10.36 2.59 0.00 0.38 -45.21MOM 26.16 -45.79 14.53 25.39 7.69 -1.44 0.57 -80.36RMW 12.19 -17.57 3.33 7.76 11.45 -0.45 0.43 -39.17CMA 9.51 -6.81 4.11 6.87 1.83 0.38 0.60 -17.30BAB 12.89 -15.22 10.90 11.92 3.22 -0.67 0.91 -52.03
Table 8Autoregression of monthly realized volatilities
The realized variances of each factor represent the sum of factor squared daily returns
in each month. The factors are betting-against-beta (BAB) and momentum (MOM).
The AR(1) process regresses the (non-overlapping inverse of the) factor monthly realized
volatility on its own lagged value. Heteroskedasticity-adjusted t-ratios are presented in
parentheses. OOS R2(%) denotes the out-of-sample (OOS) R2, which relies on an initial
(in-sample) window of 120 months. The sample period is from 1963:12 to 2015:12. Bold
t-ratios indicate statistical significance at the 5% level.
Factor ρ0 ρ1 R2(%) OOS R2(%)(t-stat) (t-stat)
BAB 12.96 0.78 60.79 63.36(7.49) (23.88)
MOM 7.16 0.75 56.11 60.41(9.12) (25.31)
33
60 65 70 75 80 85 90 95 00 05 10 15 200
10
20
30
40
50
60
70
80
90
Fig. 2. Realized volatility of BABThis figure plots the time-series of the annualized realized volatility (in %) associated
with the BAB factor computed from daily returns each month. The sample is 1964:01
to 2015:12.
34
Table 9Volatility-return tradeoff
The realized variances of each factor represent the sum of factor squared daily
returns in each month. The factors are betting-against-beta (BAB) and momentum
(MOM). The monthly return of each factor is regressed on the lagged (non-overlapping
inverse of the) factor monthly realized volatility. Heteroskedasticity-adjusted t-ratios are
presented in parentheses. OOS R2(%) denotes the out-of-sample (OOS) R2, which relies
on an initial (in-sample) window of 120 months. The sample period is from 1963:12 to
2015:12. Bold t-ratios indicate statistical significance at the 5% level.
Factor γ0 × 100 γ1 × 100 R2(%) OOS R2(%)(t-stat) (t-stat)
BAB 0.72 0.00 0.03 −0.45(1.67) (0.38)
MOM 0.43 0.03 0.41 0.00(0.47) (1.36)
Table 10Performance of scaled factor strategies: components of variance
The performance of the scaled betting-against-beta factor (BAB*) is compared
with momentum (MOM*). Each scaled factor uses the realized variance in the previous
month, and its specific and systematic components, to scale the exposure to the original
factor. The total variance is decomposed on its specific and systematic components
based on the CAPM pricing equation. All statistics are computed with monthly returns.
Reported are the maximum and minimum one-month returns observed in the sample,
the mean average excess return (annualized), the (annualized) standard deviation of each
factor, excess kurtosis, skewness, (annualized) Sharpe ratio, and the maximum drawdown
(MDD). IR denotes the (annualized) information ratio of the scaled factor with respect
to the unscaled benchmark. The sample returns are from 1964:01 to 2015:12. The max,
min, mean, standard deviation and maximum drawdown are in percentage points.
Factor Max. Min. Mean S.D. Kurt. Skew. Sharpe IR MDDPanel A: BAB*
Total 18.36 -28.14 23.60 17.89 2.08 -0.26 1.32 1.01 -57.90Specific 23.47 -45.73 30.13 24.93 3.83 -0.67 1.21 0.82 -75.07
Systematic 28032.09 -147.31 684.20 3898.63 610.79 24.68 0.18 0.15 -29202.68Panel B: MOM*
Total 24.86 -17.47 20.55 18.87 1.17 -0.02 1.09 0.93 -40.51Specific 26.70 -21.16 24.49 22.83 1.26 -0.12 1.07 0.92 -54.16
Systematic 413.05 -22164.70 -299.27 3080.05 615.07 -24.80 -0.10 -0.29 -38579.63
35
1 2 3 4 5−10
0
10
20
30Panel A: Mean(%)
MOMBAB
1 2 3 4 50
20
40
60Panel B: Volatility(%)
MOMBAB
1 2 3 4 5−1
0
1
2Panel C: Sharpe ratio
MOMBAB
Fig. 3. Conditional performance of BAB and MOMThe returns of each factor are sorted on quintiles based on the realized volatility in the
previous month. The figure presents the following annualized average return, volatility,
and Sharpe ratio. The sample is 1964:01 to 2015:12.
36
60 65 70 75 80 85 90 95 00 05 10 15 200
1
2
3
4
5
6
7
MOM*BAB*
Fig. 4. Weights of scaled BAB and MOMThis figure plots the time-series of the weights associated with the scaled BAB and MOM
factors. The sample is 1964:01 to 2015:12.
37
60 65 70 75 80 85 90 95 00 05 10 15 20−3
−2
−1
0
1
2
3
MOM*BAB*
Fig. 5. Betas for BAB and MOMThis figure plots the time-series for the realized market beta associated with the BAB
and MOM factors. The sample is 1964:01 to 2015:12.
38
Table 11Autoregression of the components of realized volatilities
The realized variances of each factor represent the sum of factor squared daily
returns in each month. The total variance is decomposed on its specific and systematic
components based on the CAPM pricing equation. The factors are betting-against-
beta (BAB) and momentum (MOM). The AR(1) process regresses the (non-overlapping
inverse of the) factor monthly realized volatility (or each of its components) on its own
lagged value. Heteroskedasticity-adjusted t-ratios are presented in parentheses. OOS
R2(%) denotes the out-of-sample (OOS) R2, which relies on an initial (in-sample) window
of 120 months. The sample period is from 1963:12 to 2015:12. Bold t-ratios indicate
statistical significance at the 5% level.
Volatility ρ0 ρ1 R2(%) OOS R2(%)(t-stat) (t-stat)
Panel A: BABTotal 16.72 0.74 54.82 57.06
(8.09) (20.89)Spec. 26.96 0.68 46.13 47.46
(10.17) (20.30)Syst. 930.83 −0.00 0.00 −0.15
(1.54) (−0.01)Panel B: MOM
Total 9.38 0.70 49.05 55.19(9.75) (21.48)
Spec. 11.81 0.68 46.11 50.42(10.81) (22.45)
Syst. 210.73 −0.00 0.00 −0.50(6.62) (−0.11)
39